Cartridge for below-surface treatment of molten metals



May 1, 1951 s, T 2,550,735

CARTRIDGE FOR BELOW-SURFACE TREATMENT OF MOLTEN METALS Filed Aug. 2,1947 2 Sheets-Sheet 1 fly-:36

Patented May 1, 1951 CARTRIDGE FOR BELOW-SURFACE TREAT- MENT OF MOLTENMETALS Sam Tour, New York, N. Y., assignor to Julius S. W. Bates,Phoenix, Ariz.

Application August 2, 1947, Serial No. 765,751

3 Claims. (01. 75--93) This invention relates to new and usefulimprovements in the below-surface treatment of molten metals.

In the conventional purification of molten metals such as degasification(elimination of oxygen, carbon oxides, hydrogen and nitrogen),

the elimination of stable oxides, and desulfurizaand up to now efficientways of adding these additives have not been found.

One of the difiiculties resides, inter alia, in the fact that theadditive material, being lighter (at the bath temperature) than themolten metal to be treated will remain on the surface of the bath andwill thus not reach the bulk of the material to be treated. Attemptshave been made to remedy this by securing the additive to the end of arod and plunging the same into the molten metal, thus pushing itunderneath the surface thereof. This is extremely hazardous,particularly when the addition agent is one of high reactivity.

Alternatively, cored solid pieces of metal basically of the compositionof the molten metal bath, and in which the cores are composed of theaddition or treating agent, have been used. In this case, the compositeis selected sufficiently heavy so that it initially will sink below thesurface of the metal bath with the hope that it will there release thetreating agent. This desideratum, however, is not achieved. If the coredpiece is open to the outside, such as an open ended tube, the majorportion of the charge will have been released by the time the piece hassunk an appreciable depth. If the cored piece is substantially closed,such as a tube with crimped or plugged ends, in which case dissolutionof the body of the piece by the molten metal bath is relied upon forrelease of the charge, such release is effected substantially at thesurface of the bath. This is by reason of the fact that, as the body ofthe composite is dissolved away by the molten metal bath, the ratio ofcore cavity to body of the composite reaches a point at which sinkingtakesplace no longer. As some of the body is dissolved away, thecomposite will begin to rise towards the surface of the molten metalbath. When sufficient of the body material has been dissolved away toexpose the additive in the corecavity or release the same to the metalbath, such part of the composite as then remains will have risen tosubstantially the bath surface.

One object of the instant invention comprises inter alia an improvedcartridge capable of discharging or exposing an additive at an effectivetreating level below the surface of a molten metal bath.

Another object of the invention comprises such a cartridge with atime-fuse capable of dissolvv ing away, thereby exposing or releasingthe additive to the metal bath, in advance of excessive dissolution ofthe body of the cartridge.

The foregoing and still further objects of the invention will beapparent from the following description'read in conjunction with thedrawings representing preferred embodiments of the invention in which:

Fig. 1 represents a cross-sectional cut through an open treatingcartridge;

Fig. 2 is a cross-section through a loaded, hermetically closedcartridge in accordance with the invention;

Figs. 3 and 319 show cross-sections through indented sealing discs for atreating cartridge;

Fig. 4 is a top view of the construction shown in Fig. 1;

Figs. 5 and 5b are fragmentary cross-sections illustrating alternativeforms of cartridge construction;

Fig. 6 shows a cross-sectional view of part of a further alternativeform of construction;

Fig. '7 is a bottom view of the cartridge illustrated in Fig. 6;

Fig. 8 represents a bottom view of an alternative indented bodyconstruction of a cartridge, and

Fig. 9 is a cross-sectional view illustrating the sealing of a preferredform of cartridge.

The treating cartridge in accordance with the invention is provided witha time-fuse arrangement defined by a mass of dissolvable materialextending between the core cavity and the outer surface of the cartridgeand having a predetermined thickness to be substantially dissolved awayin advance of the body of the cartridge. The predetermined thickness ofthe mass of dissolvable material is so selected for-a given bath andcombination of materials that it will not have dissolved awaysubstantially earlier than the point at which the cartridge has sunk toan effective treating level within the molten metal bath and not laterthan the point at which the body of the cartridge has been dissolved toan extent which will cause it to rise towards the surface of the moltenmetal bath.

Referring to Figs. 1 to 4 of the drawings, I represents the body of atreating cartridge which may be of any desired form or configuration. Itispreferred, however, to have a substantially cylindrical cartridge.cavity 2 is provided opening onto recessed portion 3. The conical base2a of the core ca vitymay constitute as much as of the volume of thecavity. The quantity of core. material charged.

or placed into the core cavity does not fill it com.- pletely. Sincemany treating materials used have higher coefficients of expansion thanthe solid material of which the cartridge is made, it has been foundnecessary to allow spacefor some expansion to take place. This method ofproviding the expansion space by way of the conical base is a convenientone when the cavities are produced by machining. Any other methods toprovide for core material expansion may be used, such as leaving theexpansion space above or around the charge of core material. The cartridge body illustrated in the drawings can be made into the desiredshape and to the required dimensions by hobbing, hot forging ormachining. The additive agent is placed into the depression or corecavity 2. After this addition a pressure retaining disc of suitablematerial and thickness such as disc 4 (Fig. 2) is placed into therecessed portion 3. The latter defines a seat 5 upon which the disc 4rests. The recessed por tion 3 is preferably annular and when sealingthe cartridge with the core of additive agent 6 in position, a suitabletool, such as a punch 8 (Fig. 9) of an outside diameter larger than thediameter of the recessed portion 3 is then forced into the top of thecontainer, thereby forming from the sides of the recess the sealing ringof displaced metal portion la over and onto disc 4 to press the sameagainst seat 5 and thereby establishing a seal. The punch is designed ofsuch size and the depth to which it is pressed in is such that thedisplaced metal I (Fig. 2) above the disc 4 is of sufiicient thicknessand has sufficient overlap to give the desired pressure retainingstrength to the assembly. The relation of the original recess to theultimatelyjformed substantially annular metal portion, displaced by thepunch from the sides of the recess, is for instance illustrated by thebroken outline of Fig. 1 indicating the disc 41) and theoverlyingsealing ring 12).

The disc 4 is pressed against the seat 5 by the displaced metal portion1 with aforce suficient to obtain andmaintain a hermetical seal of the.

core opening. The displaced metal 1 acts as a sealing ring to hold thedisc 4 upon seat 5 and against any internal pressure created in the corecavity 2 by the additive treating material in that cavity.

In lieu of the disc and sealing ring construction illustrated in Fig. 2,any other suitable closure construction may be used. Thus, for instance,a threaded plug as shown in Fig. 6 may serve as a closure for thecartridge to effect a substantially hermetical seal thereof against suchinternal pressure as may be created by the treating charge in the corecavity. As there shown, plug 9- is A centrally located core.

threaded into the recessed portion of the car tridge body l2 and bearssubstantially tightly against the shoulder H. The upper portion of plug9 projecting beyond the body 12 of the cartridge is prefereablyconstituted in the form of a hex nut 53 to permit appropriate tighteningof the plug.

In the illustration of Fig. 2, the time-fuse in accordance with theinvention is constituted by the mass of material underlying the exposedarea 4a of disc 4. When submerged in a molten metal bath the exposedmass of disc material will progressively dissolve in the manner as forinstance indicated in the dotted outlines. It will finally dissolve toan extent where a sufiicient mass has been completely dissolved away tosubstantially open the core cavity. The core material 6 can then reactwith the molten metal of the bath. To the extent that internal pressurehas built up within the core cavity, and particularly when using amaterial vaporized at the treating temperature, rupture will occur ofthe thinned disc portion before complete dissolution of any areathereof.

In lieu of the solid disc 4 an indented disc such as shown in Fig. 3 andcarrying indent I4 may be used. In this case the mass of dissolvablematerial defining the time-fuse is the portion overlying the indent.Only a relatively small amount of dissolution of the disc material isnecessary for effective opening of the core material by way of theindent ill. The use of an indent has the additional advantage that it ispossible to better control thetype. and size of injector orifice. Thisis especially of advantage when using additives vaporizable at thetreating temperature of the moltenmetal. In such case controlled gradualrelease. of treating material vapors (normally under relatively highpressure) is desirable. In such cases it is preferred to provide anindent defining a jet opening upon the dissolution of the overlyingmaterial andto choose an indent of sufficient depth. to assure that thejet opening will not become unduly distorted by the dissolving action ofthe molten metal bath and/ or the vapor pressure within the cartridgecavity.

of the core cavity. This indent leaves a relatively.

small overlying mass of dissolvable material. When the body 4 Sci thiscartridge commences to dissolve the mass of dissolvable materialoverlying. the indent i5 will rapidly thin to a point where it will openthe indent defined aperture to the core cavity considerably inadvance'of any appreciable dissolution of the. body of the cartridge.

A further alternative form of providing a suitable time-fuse isillustrated in Figs. 6 and '7. As there shown the bottom of thecartridge I1 is provided with a substantially annular inent I8 insubstantial alignment with the lower portion of the core cavity l9. Alsoin this case a comparatively small amount of dissolution ofthe body l2of the cartridge will cause an open-' ing to be established through theindent lB-to -In all cases care should be taken that the cartridge orany part thereof including the dissolvable material defining thetime-fuse is basically substantially the same as the metal of the bathto be treated, i. e., compatible with and nondeleterious to the bathmetal. a

In order to assure substantially self-submergence of the treatingcartridge the percent volume of its core cavity should be less thansubstantially progressive dissolution of the body of the cartridge inthe metal bath being treated, the percent volume of the core cavityreaches a value greater than the one just mentioned, the cartridge willcommence to rise. The dissolvable material therefore shouldsubstantially dissolve for effective cavity or core exposuresubstantially in advance of this point. On the other hand, the thicknessof the dissolvable material should be such that the same is notsubstantially dissolved away prior to the time required for the sinkingof the cartridge to an effective belowsurface treatment level within themolten metal bath.

The maximum 'mass of dissolvable material defining the time-fuse, andwhich will dissolve away for exposure of the core cavity, should be suchin relation to the core that the combined weight of the core materialand of such dissolvable material is not greater than the difference inweight between the cartridge and the volume of the molten metal of thebath displaceable by the cartridge. If such combined weight were lessthan said weight difference the dissolving material would besufilciently large to offset the maximum percentage volume of the corecavity as expressed in the above formula to a point where the cartridgewould commence to rise before satisfactory exposure of the core materialhas been obtained.

Little is known about the strength and ductility of many of the commonmetals at temperatures just below their melting points. Little is knownabout the rate of dissolution for soild pieces of metal in molten metalof basically similar composition at various temperatures above theirmelting points. For this reason, it is not possible to calculate inadvance for any given combination the thickness of the dissolvablematerial defining the time-fuse. The same, however, may beempiricallydetermined for each given combination. Such empirical determination maybe carried out for instance by preparing a number of cartridges loadedwith a desired treating charge and identical in all respects except asto thickness of the dissolvable material defining the time-fuse which isselected different in each case.

The different cartridges are then each tested by addition to a test bathof the molten metal to be treated. If a turbulent, spattering orlocalized. reaction is observed by way of ebullition of the surface therelease of the core material has taken place at or near the surface. Ifon the other hand the surface ebullition is of a controlled gradual welldistributed nature the release of thecore material has taken place at adepth satis-- factory for the desired treatment, i. e., at the effectivetreating level for said bath. The thick-- ness of the dissolvablematerial, which produced. the last mentioned surface ebullition is thecorrect thickness for that combination.

When using in the preparation of a treating cartridge in accordance withthe invention a seal-- ing disc and a sealing ring as for instanceillustrated in Figs. 2 and 9, it is important that thedisc is held bythe sealing ring onto the seat with. sufficient force to overcome anyinternal pressure that may be created in the core cavity by the:additive treating material in the cavity before exposure of the cavityby the dissolution of the meltable material constituting the time-fusein accordance with the invention.

Broadly speaking, the invention thus embraces, in combination with atreating cartridge of the hermetically closed, self-submerging type forthe treatment of molten metals and having a core cavity containing acharge of treating material, at least one time-fuse defined by a part ofsaid cartridge and comprising a mass of dissolvable material extendinbetween said core cavity and the outer surface of said cartridge and ofa predetermined thickness to be substantially dissolved away, by themolten metal bath to be treated, within a period of time not less thanthat required for the sinking of said cartridge to an effective treatinglevel within said bath and not substantially more than that required forthe percent volume of said cavity to have increased to the point wherethe entire cartridge rises.

In all cases, the hermetical seal should outlast the time required fordissolution of the meltable material to the extent necessary to open thecore cavity within the limiting conditions herein stated. A satisfactoryseal, therefore has a thicker section than the time fuse section.

The expression dissolve away or similar term used herein in connectionwith the removal of dissolvable material to effectively expose the corecavity of a cartridge in accordance with the invention, includes thelimiting case in which at least part of the meltable material is ejectedinto the molten metal of the bath in substantially molten or at leastheat softened condition by any pressure created by the core material atthe temperature of the molten metal bath. Such ejection may particularlyoccur in connection with the use of a core material which willsubstantially vaporize at or below the temperature of the metal bath tobe treated.

When the treating cartridge in accordance with the invention is added toa molten metal bath for the treatment thereof, it will sink below thesurface due to the predetermined greater specific gravity of thecomposite. In View, however, of the chilling effect of the cartridge, acertain amount of crust formation occurs which is undesirable. I havefound that it is possible to alleviate such crust formation to a largeextent by providing the cartridge in accordance with the invention witha heat retarding or insulating material such as a coating of ceramic orsimilar matter. I have found that the use of such an insulating materialreduces the rate of dissolution of the container in the molten metal asst-es a lbwj it mt-re. t me to is s ifallyi advantageous. when treatinglarge deep baths of moltenmetal,

When, using a cartridge or the substantially self-submerging typedescribed in accordance with the invention, though the same willinitially sink, the specific gravityof the composite'chang'es at timesso rapidly by the partial melting of cartridge exterior, that the samemay soonstart to: rise towards the surface without having re maimed atthe desired effective bathle'vel afsuflicient time for sa'tis'factoryrelease of charging material. overcome this condition by the use oiacartridge having a' core cavitynot exceeding substantially (l -d; 13d;

v lume of the body f a Cart dselds in th specific gravity of the metal,ofthe cartridjge body when ome at its melting point and'd'e. being the.

specific gravity of the metal of thebody' 9f the cartridge at itsfreezing point when molten. Such a cartridge equipped with a suitableclosure such as a disc of proper thickness irrespective of the materialconstituting the core will always sink' and remain at a sufiicient'depth below the surfac up to the time at which the release of chargingmaterial as 'iorinstance controlled by the disc thickness, is efiected,For most pur-- poses I find that a core cavity correspondingsubstantially to -7% by volume of the body of the cartridgewillsubstantially satisfy this for.-

mula and will constitute a universally usable car tridge for themajority of the conventional molten metal bath treating materials of thekind and type herein mentioned.

V'IThe' foregoing description is for purposes of illustration and not oflimitation and it is my intention therefore that the invention belimited only by the appended claims or their equivalents wherein'I haveendeavored to claim broadly all inherent novelty.

I claim:

1. A cartridge for the treatment of aniolten metal with arelativelysmall amountof a treating agent of lower specific. gravitythan said metal, consisting'o'f a'metal container defining andcompletely enveloping a cavity, a charge of said treating agent withinsaid cavity, a minor section of the wall of said cavity being relativelyI have found that I can satisfactorily thin n'n dboi atq teem-net the r'm ide f;- se d. al be n 'r ti qly thick. and hea y. the e ifghtf oithecontainer and charge exceeding the weightoi a, ,corresponding volume inliquid state; ofthe metal of which the container is composed.

2 ,A. ca rtridg:e for the treatmentota molten metal with av relativelysmall amount of a treat- ,ing agent of lower specific gravity than-said.10

metal, consisting of a metal container defining and-, om let ly en lping a y. said cavity having a volume equal to 5, 7% of the volume ofthe, body of the cartrid e, a charge of said treating agent within saidcavity a minorsection of the wall of the container being relatively thinin, proportionto the. remainder, the remainder of. said. wallbeing'relatively thick and heavy, the. weight Off the container; andcharge exceeding the'weight of a corresponding volume in liquid state ofthe metal of which the container is composed.

3. A cartridge for the treatment of a, molten metal with a relativelysmall amount. of a treat-. ,ing-"agent'of lower specific gravity thansaid metal, consisting of a cylindrical metal container defining andco'mpletely enveloping a centrally located cylindrical cavity, a chargeof said treating agent within said cavity, a minor section of .the wall'of said ccntainerbeing relatively thin in proportion to, theremainder, the remainder o'fjsaid Wall being relatively thick and heayythe weight of the container and charge exceeding the, e h of es olnd nvolume. in liquid state ;of the metal of which the container iscomposed.

SAM TOUR.

7 REFERENCES CITED" 'iheLfollowing references are of record in the

1. A CARTRIDGE FOR THE TREATMENT OF A MOLTEN METAL WITH A RELATIVELYSMALL AMOUNT OF A TREATING AGENT OF LOWER SPECIFIC GRAVITY THAN SAIDMETAL, CONSISTING OF A METAL CONTAINER DEFINING AND COMPLETELYENVELOPING A CAVITY, A CHARGE OF SAID TREATING AGENT WITHIN SAID CAVITY,A MINOR SECTION OF THE WALL OF SAID CAVITY BEING RELATIVELY THIN INPROPORTION TO THE REMAINDER, THE REMAINDER OF SAID WALL BEING RELATIVELYTHICK AND HEAVY, THE WEIGHT OF THE CONTAINER AND CHARGE EXCEEDING THEWEIGHT OF A CORRESPONDING VOLUME IN LIQUID STATE OF THE METAL OF WHICHTHE COSNTAINER IS COMPOSED.